Many current millimeter-wave antennas have efficiencies of fifty-percent or less. In the case of antennas used for high-power transmission, these low-efficiencies may result in a significant amount of input power being absorbed by the antenna structure and converted to heat. Furthermore, these low efficiencies require much higher input power levels.
Another problem with current millimeter-wave antennas is that manufacturing techniques make it difficult to precisely fabricate an antenna with particular performance characteristics and for a particular millimeter-wave frequency. This is especially a problem when the frequency and performance characteristics of the antenna need to be substantially identical or matched with other antennas, for example, when more than one antenna is combined with other antennas.
Thus, there are general needs for more efficient millimeter-wave antennas. There are also general needs for millimeter-wave antennas that can be precisely manufactured with predictable frequency and performance characteristics.